Pathogens can be dangerous to the public. For example, Enterohemorrhagic Escherichia coli O157:H7 (E. coli O157:H7), a foodborne pathogen, is a facultative gram-negative bacillus that is dangerous and has been implicated in outbreaks of illness due to ingestion of meats, water, and uncooked fruits and vegetables. E. coli O157:H7 is capable of producing a variety of human illnesses which include hemolytic uremic syndrome and diarrhea. The outbreaks of E. coli O157:H7 food poisoning in the US over the past few decades and the sporadic worldwide outbreaks caused by contaminated ground beef has raised growing interest in rapid pathogen identification.
Current methods for detecting foodborne pathogens are time consuming and not very sensitive. Traditionally, detection of foodborne pathogens has involved sample collection, enrichment, followed by isolation and identification of the targeted organism by a variety of methods. The current methods capable of foodborne pathogen detection include traditional enrichment and plating methods in selective media, polymerase chain reaction (PCR), fiber optic biosensors, immuno-magnetic beads, and quartz crystal microbalance (QCM). Each of the stated methods has its own set of limitations. Enrichment and plating approach lack sensitivity and specificity, and often takes 24-96 hours to identify the contaminant organism. Most immuno-magnetic assays and fiber optic biosensors require pre-enrichment of the sample since the pathogenic bacteria is present in concentrations below the technology's limit of detection. In addition to sample enrichment requirements, PCR methods have a higher cost, and require well-trained personnel. QCM analysis is not very sensitive and, therefore its use is limited when pathogen is present at high concentration with a high level of contaminants. In addition to the individual limitations, the current methods of food sampling do not ensure 100% absence of unwanted, potentially cross-reactive, contaminants due to the intrinsic nature of sample collection.